Volatile organic compounds are known to pose health and environmental hazards. On the one hand, ozone depletion and global warming are now attributed to such factors as the release of copious quantities of chlorofluorocarbons (CFC's) and similar volatile compounds. On the other hand, inhalation of volatile constituents, particularly solvents or similar compounds used in a wide range of manufacturing procedures, is known to result in potentially severe health hazards. In all such cases, the characteristics which make these compositions particularly desirable in manufacturing procedures, such as the efficacy of a composition as a solvent or cleaning agent (e.g., volatility), are directly responsible for the deleterious or potentially deleterious effects accompanying their use.
Systems have been devised to minimize solvent loss during or incident to procedures in which these volatile compositions have a tendency to escape to the atmosphere. Some are recovery systems designed to retrieve the fluid and entrained materials resulting from a manufacturing procedure, such as a cleaning procedure, and thence separate the reusable fluid from contaminants. These systems tend to have common limitations or drawbacks. For example, air is often allowed to enter the system and mix with vapor, whereupon removal of the air necessarily implicates loss of volatile constituents as well. More direct sources of solvent loss may be attributed to diffusion, "dragout," and system leaks.
Indirect solvent loss, as in the case of solvent admixed with admitted air, has been addressed most commonly by means of carbon absorbers. Those recovery or control systems can become complicated and hence costly in terms of both capital investment and operating expense. Direct loss is sometimes easier to control, but many potential solutions designed for that purpose can contribute to admission of ambient air to the system, resulting in the types of problems mentioned above. Thus, it is not uncommon to find solvent systems used in, for example, the electronics industry for cleaning printed circuit boards or electronic components, to emit relatively large amounts of solvent vapor, on the order of 8 to 10 pounds of solvent per hour.